Electronic States in Magnetic Semiconductors –An Extension of CPA to Random Spin Systems–

Abstract

Electronic structure in magnetic semiconductors is investigated on the basis of the s - d exchange model. The exchange scattering of an electron by localized spins is treated in the coherent potential approximation. Coupled equations for the down- and up- spin Green functions are obtained. These equations agree in the weak s - d interaction limit with the results of the molecular field approximation and in the strong interaction limit with those obtained previously by the present author. The density of states for down- and up- spins is calculated in the paramagnetic and completely ferromagnetic states for various values of interaction strength, by assuming a semi-elliptic form for unperturbed density of states.